.TH std::shared_future::valid 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::shared_future::valid \- std::shared_future::valid

.SH Synopsis
   bool valid() const noexcept;  \fI(since C++11)\fP

   Checks if the future refers to a shared state.

   This is the case only for futures that were not default-constructed or moved from.
   Unlike std::future, std::shared_future's shared state is not invalidated when get()
   is called.

   The behavior is undefined if any member function other than the destructor, the
   copy-assignment operator, the move-assignment operator, or valid is called on a
   shared_future that does not refer to shared state (although implementations are
   encouraged to throw std::future_error indicating no_state in this case). It is valid
   to move or copy from a shared_future object for which valid() is false.

.SH Parameters

   \fI(none)\fP

.SH Return value

   true if *this refers to a shared state, otherwise false.

.SH Example


// Run this code

 #include <future>
 #include <iostream>

 int main()
 {
     std::promise<void> p;
     std::shared_future<void> f = p.get_future();

     std::cout << std::boolalpha;

     std::cout << f.valid() << '\\n';
     p.set_value();
     std::cout << f.valid() << '\\n';
     f.get();
     std::cout << f.valid() << '\\n';
 }

.SH Output:

 true
 true
 true

.SH See also

   wait waits for the result to become available
        \fI(public member function)\fP
